a) Field of the Invention
This invention relates to a cleaning apparatus for removing dirt or particles from at least one surface of a substrate or sheet, on which the dirt or particles have deposited in a fabrication process thereof, by capturing the dirt or particles on a tacky rubber roller having tackiness and then transferring the dirt or particles onto an adhesive tape roll, and especially to a pressing control mechanism for the tacky rubber roller and adhesive tape roll, said pressing control mechanism being useful in the cleaning apparatus. This invention is also concerned with a substrate or sheet surface cleaning apparatus in which a tacky rubber roller can be assured to always remain at a surface thereof in close contact with a surface of substrate or sheet irrespective of the passing state, thickness or the like of the substrate or sheet.
b) Description of the Related Art
A substrate or sheet surface cleaning apparatus is provided with a tacky rubber roller having tackiness and an adhesive tape roll to remove dirt or particles from a surface of a substrate or sheet, on which the dirt or particles have deposited in a fabrication process thereof. It has been considered necessary to urge the adhesive tape roll against the tacky rubber roller and further to urge, under pressing force of the adhesive tape roll, the tacky rubber roller against the surface of the substrate or sheet such that the tacky rubber roller can be maintained in close contact under constant pressure with the surface of the substrate or sheet to facilitate the capture of the dirt or particles onto the tacky rubber roller and the dirt or particles captured on the tacky rubber roller can be surely transferred onto the adhesive tape roll. To control the pressing force from the adhesive tape roll, a pressing control mechanism is built in the cleaning apparatus. This pressing control mechanism generally makes use of air cylinders, each of which in turn uses as a power source compressed air supplied from an air compressor; solenoid-operated valves; torque motors; or the like.
Use of such air cylinders, however, requires pressure-reducing adjustments to obtain optimal pressures at the tacky rubber roller and adhesive tape roll employed in the cleaning apparatus, leading to a drawback that the operator is required to perform very irksome adjustments.
To supply compressed air as a power source for the air cylinders, it is necessary to install an air tank in addition to an air compressor. The space required for the installation of these air compressor and air tank reduces the working space, and moreover, their installation leads to an increase in the initial cost.
Further, such air cylinders tend to cause over-pressing due to their characteristic that cylinder rams are pushed to full extent by compressed air. As a consequence, there are significant potential problems in that a precise substrate such as LCD, from which dirt or particles deposited on a surface thereof is to be captured, transferred and removed when the precise substrate is caused to pass in close contact with the tacky rubber roller, may be damaged and the tacky rubber rollers themselves may also be damaged.
Use of the solenoid-operated valves, torque motors or the like, on the other hand, cannot carry out precise pressing control at elevated temperatures, because the performance of the solenoid-operated valves, torque motors or the like is reduced at such elevated temperatures. To avoid such a reduction in performance at elevated temperatures, a cooling system is additionally required for the solenoid-operated valves, torque motors or the like as the power source for the pressing control. In addition, precise control of pressing also requires precise control of power to be produced by these solenoid-operated valves, torque motors or the like. A complex electric power control circuit is therefore needed for obtaining a constant power output, leading to a still further drawback that the use of the solenoid-operated valves, torque motors of the like is very disadvantageous from the standpoint of the maintenance of the electric power control circuit and the running cost required for this maintenance.
A pressing control mechanism for tacky rubber rollers and adhesive tape rolls--which are used in a cleaning system in which dirt or particles deposited on opposite surfaces of the substrate or sheet during its fabrication process are captured by the tacky rubber rollers having tackiness and are then transferred and removed as described above--generally performs control over the entire tacky rubber rollers and adhesive tape rolls, in other words, performs control with the premise that pressing forces at opposite ends of the tacky rubber rollers and adhesive tape rolls become constant. If the substrate or sheet, i.e., the material under treatment passes between the tacky rubber rollers with its position extremely shifted either leftward or rightward relative to its advancing direction and especially when the substrate or sheet has a large thickness in the above situation, the tacky rubber rollers are caused to tilt by the passing substrate or sheet. As a result, the close contact of the tacky rubber rollers with the substrate or sheet may become uneven in the direction of axes of the tacky rubber rollers. Described specifically, each tacky rubber roller and the opposing surface of the substrate or sheet may therefore fail to come into close contact with each other and a space may be formed between them, although the tacky rubber roller should be brought into close contact under constant pressure with the opposing surface of the substrate or sheet. Accordingly, dirt or particles which deposited on the surface of the substrate or sheet in its fabrication process may not be fully removed.
The uneven close contact of the tacky rubber rollers with the substrate or sheet, which takes place as described above, lowers the surface treating ability of the tacky rubber rollers for the substrate or sheet and further, brings about another problem that, upon transferring and removing captured dirt or particles from the surfaces of the tacky rubber rollers onto the associated adhesive tape rolls by relying upon the close contact between the adhesive tape rolls and their corresponding tacky rubber rollers, the removal may not be effected fully.
With a view to avoiding such uneven close contact of the tacky rubber rollers against the substrate or sheet, it may be contemplated to arrange built-in pressing control mechanisms--each of which makes use of an air cylinder employing as a power source compressed air supplied from an air compressor, a solenoid-operated valve, a torque motor or the like--at opposite ends of the tacky rubber rollers and adhesive tape rolls and then to adjust pressures applied to the opposite ends of the tacky rubber rollers and adhesive tape rolls such that the surfaces of the tacky rubber rollers can be always maintained in fully close contact with the corresponding surfaces of the substrate or sheet. The arrangement of such built-in pressing control mechanisms, however, involves drawbacks such as a substantial increase in manufacturing cost, a reduction in working efficiency due to a need for irksome adjustments, and a significant disadvantage to maintenance work.